Measurement of areal density modulation of laser-imploded shells through K-edge imaging.

A new method for studying the modulations in the ρΔR of imploded shells is introduced: using a recently developed pinhole-array x-ray spectrometer, core images are obtained at energies below and above the K-edge energy of a titanium dopant. The ratio of these images reflects the nonuniformity of the cold shell around the time of peak compression, independently of modulation in core emission. The two-dimensional images of ρΔR modulations are of interest in laser fusion because they show the final result of unstable implosion evolution. The measured average ρΔR of the cold shell and the amplitude and spectrum of its modulations are in agreement with the results of two-dimensional code simulations that include imprinting of laser nonuniformity on the target. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]